USB: ohci_usb can oops on shutdown

When ohci-hcd is shutting down (for rmmod or PC-card removal), there is
a window when the device is shut down, HC communication area (->hcca)
is freed, but the core has not called "free_irq" yet. If another device
triggers a shared interrupt in this window, we oops when trying to
access the freed ->hcca.

This patch removes the window by calling free_irq before ->hcca is freed.

The patch is tested at the PC hotplug test rig at Stratus, and with
rmmod by Rafael Wysocki.

Signed-off-by: Pete Zaitcev <zaitcev@redhat.com>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>